This invention relates to improvements in steering column assemblies of the kind which include a steering lock mechanism and which may be fitted to road vehicles and the like.
Steering assemblies are well known in which a steering wheel is connected to one or more road wheels of a vehicle to enable a driver of the vehicle to steer. The steering assemblies generally include a steering column assembly which includes a steering shaft that is supported within a steering column shroud. The shaft is connected at one end to the steering wheel, either directly or indirectly, and at the other end is connected through steering gear to the road wheels of a vehicle. As the driver turns the steering wheel the shaft turns within the shroud, and this causes the road wheels of the vehicle to turn to provide steering of the vehicle. The rotation of the shaft by the driver may be assisted by a hydraulic or electric power source to provide a power assisted steering system, or the steering may be unassisted.
The function of the shroud is to support the steering shaft. It typically comprises a generally elongate, hollow, casting within which the steering shaft extends. It may be in one or two or more parts, and may be generally tubular. The shroud is fixed to a solid part of the vehicle through a mounting bracket, and may in some cases be permitted to move relative to the mounting bracket to permit adjustment of the position of the shroud as required during reach and rake adjustment of the steering wheel. A clamp mechanism permits the shroud to be locked in a preferred position relative to the mounting bracket once adjusted by the driver.
It is also common to fit a steering lock to the steering column assembly which, when locked, acts between the steering column shroud and the steering shaft to prevent rotation of the steering wheel. When unlocked the steering lock permits the shaft to rotate within the shroud. Typically the lock mechanism comprises a lock bolt which may project from a lock mechanism through an opening in the shroud to engage the steering shaft. This helps to prevent theft of the vehicle by immobilising the steering shaft. For convenience the lock is usually bolted to the shroud just below the steering wheel where it can be conveniently locked and unlocked by operation of the ignition key of the vehicle. In some modern vehicles the lock is an electric lock such as a solenoid and locks and unlocks in response to control signals from the vehicle electronic management system.
Unfortunately it is not uncommon for a thief to damage the lock mechanism in order to try to steal the vehicle. There are many forms of attack, but the most common is a brute force attack in which the thief attempts to smash the lock mechanism away from the steering column by striking it with a heavy object such as a hammer. Due to the limited space for accommodating the lock mechanism it is difficult to make the mechanism sufficiently massive and robust to resist this form of attack for a long period of time.